I'm just wondering about dimensions on the pannel with the door zipper. It will be on one of the short triangles, just right of the trekking pole. I was intending to lay the zipper on the cut pannel a few inches to the side of the seam near the trekking pole and just sewing it on (prior to assembly!). I would then cut the fabric up the centre of the zip and hem it up the zip. This would leave a small raw edge at the top of the zip that I suppose I would just have to patch over. I have tried searching but cannot find much material on this tricky operation. Are there any insider secrets I should know about before I start cutting? Here's a picture of the head end, it shows where the zip will go more clearly. The inspiration for this design was from Steve Evans' All WET tarp..

Hi Rob,
the program I use is called google sketch up. It is free from google and quite a few people on these forums use it. You just draw what you want and SU tells you the dimensions. Then you just add on seam allowances and make a pattern, or cut, or whatever. I think you can get dedicated fabric design software, but judging by some of the results on this forum, it would be overkill.
Matt

Matthew – a couple ways I have done it:
1) make your cut, then at the top you cut a short 'Y shape so that yu have two short cuts at 45 degrees either way from your main cutline. Then when you sew in the zipper, having first determined the right amount to fold over and the right point on the ziper tape to line up with so that the exposed zipper equals the amount of fabric that is folded under (hope that makes sense), when you get to the top you'll have a little triangle that folds up instead of off to the side, and that finishes it off pretty well.
2) Even better is to continue your cut to the top of the fabric panel, and from the top of the zipper to the edge of the fabric, you insert a narrow strip of fabric(same width as the zipper) with a hemmed bottom end that laps down over the top end of the zipper. That gives you a cleaner termination.